Report on Suwanosejima (Japan) — March 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 3 (March 1989)
Managing Editor: Lindsay McClelland.
Suwanosejima (Japan) Explosions and ashfall; 1988 activity summarized
Please cite this report as:
Global Volcanism Program, 1989. Report on Suwanosejima (Japan). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 14:3. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198903-282030.
29.638°N, 129.714°E; summit elev. 796 m
All times are local (unless otherwise noted)
On 1, 14, and 16 January, residents . . . heard explosions. Ash fell to the S on 21 and 24 January in the the only inhabited part of the small island. On 7 February at 1225, an explosion sound was heard, and on 28 February, a 1,000-m-high ash plume deposited large amounts of ash to the S. At 1640 on 3 March, the crew of a JAS aircraft observed a 2,000-m ash cloud. A summary of [1987-88] explosions and ashfall is shown in table 2.
Table 2. Eruptive episodes at Suwanose-jima, January 1987-October 1988. Courtesy of JMA.[Skip text table]
1988 Plume Activity Height (m) Jan 05 -- Four explosions 16 300 Five explosions 17 500 Four explosions 18 300 One explosions Feb 29 -- Explosion at 1325 caused air shock Mar 08 500 Eleven explosions accompanied by air shock 28 -- Three explosions accompanied by air shock Apr 13 500 Five or six explosions per minute 14 500 40-50 explosions 15 2000 TOA Domestic Airlines pilot saw the plume rising 2000 m 16 500 Ashfall in the S part of the island Jul 18 3000 Southwest Airlines pilot saw the ash plume rising Aug 09 2000 Japan Air System pilot saw the plume rising 2000 m 13 500 Ashfall in the S part of the island 29 300 Several explosions, ashfall Oct 03 500 Ashfall in the S part of the island 06 -- Rumbling, ashfall in the S 07 -- Rumbling, ashfall in the S
Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
Information Contacts: JMA.